Automatic choke



M. J. KITTLER AUTOMATIC CHOKE Aug. 14,1951

Fil ed Nov. 19, 1949 .IMW v IN V EN TOR.

Patented Aug. 14, 1951 UNITED STATES PATENT OFFICE AUTOMATIC CHOKE Milton J. Kitt ler, Detroit, Mich., assignor to George M. Holley and Earl Holley Application November 19, 1949, Serial N 0. 128,440

1 Claim.

The object of this invention is to solve one of the problems created by the transfer of the choke valve. This response is such that thechoke as- V sumes a position to balance the suction effect on the valve of the air flow past the choke valve and past the throttle. If the existing arrangement is copied the balanced choke valve is opened only by the drop below the throttle. throttle is opened sufliciently this drop will be relatively too small to-be effective compared to the drop when the throttle is closed. I have discovered that by utilizing the drop below the choke and above the throttle I can gradually control the motion of the choke valve during the very critical period (seconds and minutes) during which time the engine warms up. The drop of pressure below the choke and above the throttle is not so sensitive to throttle position as is the suction below the throttle.' With suction below the throttle a comparatively stiff spring is needed, a lighter spring can be used with the intermediate suction.

With the existing arrangement as the throttle is closed, after the engine first fires, the build up of suction below the throttle helps to keep the choke valve open but the unbalanced choke valve tends to close as the air flow decreases due to the closing motion of the throttle.

The actual position of the choke is a resultant of these two opposing trends. To duplicate this result the effective suction to open the choke must decrease as the choke opens regardless of the position of the throttle. I have discovered that the suction derived below the choke and upstream of the throttle valve has the desired characteristics. As a result the choke assumes the position which induces just the right degree of richness to maintain the engine firing until it warms up sufficiently to release the choke 100%.

Fig. 1 shows an outside elevation, partially in section, of my invention viewed from plane l--I of Fig. 2.

If the 2 Fig. 2 shows a cross-sectional elevation on plane 2--2 of Fig. 1.

Fig. 3 shows a cross-sectional plan view taken on the plane 3-3 of Fig. 2.

Fig. 4 shows a view looking in the direction of plane 4-4 of Fig. 2.

In the figures I0 is the air entrance. l2 and M are the two rich mixture tubes which derive their fuel from the float chamber, not shown. This float chamber is supported by the flange I I. I8 is the low speed fuel outlet of the left hand unit of Fig. 2. 22 is the auxiliary low speed fuel outlet that becomes effective when the throttle 24 is opened anti-clockwise (Fig. l). Choke valves 30 and 32 are concentrically located in the venturis 3| and 33. These choke valves embrace the rich mixture tubes l2 and i4. Choke valves 30 and 32 are perforated so that whether the choke valve is opened or closed the fuel can flow down the rich mixture tubes l2 and H, as shown in my copending application Serial No. 121,545, filed October 15, 1949. 36 is an opening below the choke valves 30 and 32 which breaks into the air passages 38 and 40 downstream of the venturis 3| and 33. This opening 36 is in an inclined drilled passage 44 (Fig. 1) which transmits the suction below the choke valves 30 and 32 to the underside of the piston 48. Piston 48 is connected to intermediate choke shaft 50 by links 5| and 52. Choke shaft 54 is connected tothe throttle control mechanism as shown in Figs. 1 and 2.

A lever 58 is connected to a link 60, the lower end of which engages with a slot 62 in the fast idle cam plate 64. The plate 64 is engaged by the idle stop screw 66 mounted on the throttle lever 68, which lever is mounted on the throttle shaft 10.

A thermostat chamber '2 acts as a housing for a thermostat 14 which engages the link 16, which link engages the left hand choke shaft 18 through the lever 53. The lower end of the link 16 engages with the lever 15 (Figs. 1 and 2). Lever 15 is mounted on shaft 11. Shaft 11 carries the lever I9 which is engaged by the thermostat 14. The contraction of the thermostat 14, when cold, causes the hook 95, at the outer right hand end of the coil 14 to engage the end of the arm 19. This arm 19 is riveted to the shaft 11. The cap 99 carries the pin 91 which is split in the middle and acts as an anchor for the coil 14. Cap 99 is rotated with reference to the casting 80 so as to give the initial adjustment to the thermostat 14. When the thermostat I4 is hot the thermostat rotates clockwise and no longer engages with the arm 19. The weight of the link 18 and of the arms 5l53 and of the link 52 and of the piston 48 rotates the choke valve 80 (Fig. 1) anti-clockwise into the open position in which the chokeis shown. Choke shafts 50, 54 and Il are all connected together through the choke valves 30 and 32 as shown in my co-pending' application Serial No. 121,545, filed October 15, 1949, of which this application is a continuation in part. A hot air tube 80 supplies hot air to the chamber 12. The hot air tube 80 passes through the exhaust manifold 8| so that as the engine warms up the choke is progressively released. An air cleaner is usually connected to the entrance and to the pipe 80 or it is connected to the air entrance 10 as there is an air cleaner-silencer combination mounted on the flange I I, as set forth in co-pending application Serial No. 102,687, filed July 1, 1949.

A pipe 82 and a restriction 84, connected to the mixture outlet 83 below the throttle 24, ensures a circulation of hot air around the thermostat 14.

Operation Assume a cold engine with the choke closedafter the engine has been cranked and the engine has fired there is immediately created a suction beneath the piston 48 which tends to partially open the choke. When this occurs the reduction in suction follows until a balance is reached which 4 balance corresponds to the equilibrium of an unbalanced choke valve in the air stream of the air entrance. The link I, slot 62 and cam 64 provides the correct fast idle for a cold engine; in a well known manner.

What I claim is:

An automatic choke for an internal combustion engine having a plain tube carburetor, a mixture outlet. 9. throttle valve therein, a venturi and a butterfly choke valve in the air entrance to said mixture outlet, a choke shaft carrying said choke valve and diametrically located in the throat of said venturi, a cylinder, a passage connecting said cylinder to a point downstream of said symmetrical choke valve and upstream of said throttle valve, a piston in said cylinder connected so as to open said choke valve as the suction downstream of said choke valve and upstream of said throttle increases, a thermostatic spring adapted when cold to close the choke valve in opposition to the action of said piston in response to the suction between the throttle and the choke valves.

. MILTON J. IGTTLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,464,333 Pembroke Aug. 7, 1923 1,711,748 Schley May 7, 1929 1,996,245 Hunt Apr. 2, 1935 2,402,361 Bicknell June 18, 1946 

